It would be much easier to watch the games' replay later and take the screenshots there.
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MurchApr 20 '12 at 7:55

The question was about taking hud-less screenshots "during play". I agree that my suggestion would require a second account, and a sandboxed instance of SC2 (somewhat of a pain to set everything up), and yes it would be much easier to use a replay.
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chobokApr 20 '12 at 8:29

Yeah, the only way to take screen shots like that would either to watch it in a replay after you already played or use the map editor.
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Nick122Apr 20 '12 at 13:50